1. Field of the Invention
The present invention relates generally to non-volatile memory devices and particularly, to voltage regulators used in non-volatile memory devices.
2. Background of the Invention
Non-volatile semiconductor memory devices have become popular for use in various electronic devices. For example, non-volatile semiconductor memory (including Electrical Erasable Programmable Read Only Memory (EEPROM) and flash memory) is used in cellular telephones, digital cameras, personal digital assistants, mobile computing devices and other electronic devices.
Voltage regulators are commonly used to regulate internal voltage in non-volatile memory systems, for example, in a NAND based flash memory system. A typical voltage regulator provides an output voltage (VDD) based on an externally provided input voltage (VEXT). Typically, VDD is used by various components within the memory system.
Conventional voltage regulators have inherent drawbacks. For example, the regulated output voltage is susceptible to load current variations. In conventional systems, if a load current is lower than a specified value then the output voltage from the voltage regulator increases substantially. To limit this effect, typically, a current sink is provided at an output node of the voltage regulator. The current sink increases power consumption in the voltage regulator, which is not desirable in high-density flash memories.
Furthermore, VDD spikes during start-up operation of the memory system, because an output transistor is always on. This may cause undesirable stress for plural circuit components.
Therefore, there is a need for a method and system for better controlling output voltage in voltage regulators.